Okay, so I am getting pretty frustrated with the very first part of the Conditional Reasoning section in the LRB, specifically page 117-119, the one with John receiving an A+and all that. However, once it gets to showing you how to diagram the statement to find out if it is valid or invalid I start to get lost. What exactly is the point of this? What am I trying to do here? How do I determine what part of the statement is Sufficient and what part is the Necessary? Or is it always from left to right when reading a conditional statement?According to what I have read so far, am I looking for a "contrapositive" that reverses and negates it, which then will be the right answer? In fact, I think I am straight confused, so if anyone can just give me a quick run down of what I just read to make it clearer it'll be much appreciated

Last edited by Underdog180 on Wed Jan 12, 2011 10:11 pm, edited 1 time in total.

If you can't master conditional reasoning you will likely have a LOT of trouble with other question types. The point of these exercises is to able to translate any conditional statement into an "if A then B" form, or commonly diagrammed as A->B.

A few important applications of conditional reasoning:

1. Must Be True questions - There are often MBT questions that rely on your ability to make a transitive link between conditional statements to draw a conclusion. I.E. If A then B, and if B then C. An answer choice that says If A then C would have to be true. The problem is the stimulus will not lay out this transitive link on a platter. It will be convoluted to the extreme and you will have to rely on your ability to translate regular sentences into conditional statements.

2. Sufficient / Necessary assumption questions: If you don't have a fundamental understanding of what a sufficient or a necessary statement is, you will be completely lost in trying to figure out how to distinguish between these two question types.

3. Flaw questions - Conditional flaws appear quite frequently. Learn those invalid forms down cold if you want to get these questions right. An example: "Carla knew that if Bob was looking to get laid he would come to tonight's party. Bob is at tonight's party, so clearly he is looking to get laid." The flaw is very easy to spot if you know that converses are an invalid form. "If Bob wants to get laid -> come to party". "Come to party" does not prove he wants to get laid. The answer choice in this case would say something like "There are other reasons Bob would want to come to the party".

There are many other applications, so grind through that section and come back with more specific questions. If you can't grasp the more basic concepts you'll be in a lot of trouble in later LR sections

In the LRB, it says "If a sufficient condition occurs, you automatically know that the necessary condition occurs. If a necessary condition occurs, then it is possible but not certain that the sufficient condition occurs." So, how does this rule apply in diagraming? In terms of, Mistaken Reversal, Mistaken Negation, and Contrapositive. Also, is reversing and negating the elements the primary focus in conditional reasoning?

it took me couple reads through and practice in the Powerscore LR practice book to get a better grasp of conditional reasoning. I found it too be one of the most difficult things to grasp in the beginning but now it is much easier to pick out conditional statements and be able to diagram them with confidence. Like other posters said don't skip this section on the grounds, whats the point? I did this and caused me some problems and had to revisit it, if you can't diagram good luck getting over 160 because it is also applicable to the games section too. Good luck! One thing that really helped me is not to think of the sentence as what their describing, because the LSAC says things that reverse from what you might the average person would assume to be necessary for a sufficient condition to occur. But instead think of it as A B C. In the Beginning I would scratch out what they were describing as being a conditional, ie If a car runs then the gas must be full, with if A then B. Because I wanted to ignore thinking with common sense, which is what held me up so much (might be your problem) and think logically like LSAC wants you to. LSAC is preying upon those who think with common sense, so watch out for reversals on what you would typically would think of making sense.

Last edited by jre425 on Thu Jan 13, 2011 3:30 pm, edited 1 time in total.

Underdog180 wrote:One last question, Conditional Reasoning isn't a question type right (such as: weaken, strength, must be true)? It's just a skill that needs to be learned for majority of the questions etc?

No but its a skill that is required to do well, you use it to prove things and find inferences faster without mistakes. Used both in games and LR so could be in 75% of your test, and wouldn't hurt for RC to know too.

jre425 wrote:it took me couple reads through and practice in the Powerscore LR practice book to get a better grasp of conditional reasoning. I found it too be one of the most difficult things to grasp in the beginning but now it is much easier to pick out conditional statements and be able to diagram them with confidence. Like other posters said don't skip this section on the grounds, whats the point? I did this and caused me some problems and had to revisit it, if you can't diagram good luck getting over 160 because it is also applicable to the games section too. Good luck! One thing that really helped me is not to think of the sentence as what their describing, because the LSAC says things that reverse from what you might the average person would assume to be necessary for a sufficient condition to occur. But instead think of it as A B C. In the Beginning I would scratch out what they were describing as being a conditional, ie If a car runs then the gas must be full, with if A then B. Because I wanted to ignore thinking with common sense, which is what held me up so much (might be your problem) and think logically like LSAC wants you to. LSAC is preying upon those who think with common sense, so watch out for reversals on what you would typically would think of making sense.

Thanks man I really appreciate the advice. But when you say watch out for reversals do you mean the "Mistaken Reversal" that the LRB points out as wrong? So, then we are always looking for the contrapositive that reverses and negates? Sorry I am just on the beginning parts of the conditional reasoning in the LRB.

What I meant is by mixing up the sufficient and the necessary condition when you read a sentence. For example, if you a read a sentence that actually says A -> B (if A then B, contra positive is: if not B then Not A) as being B -> A (if B then A, contra positive is: if not A then not B) read competently different. Because the actual statement says that if A happens then you HAVE to have B, but if you have B it doesn't mean you have A or don't have A. But if you mixed the S and the N conditions around then it would read if B happens then A has to happen, but if A happens then B doesn't necessarily happen. As a result you will yeild incorrect answers because what you know as MBT (must be true) will in reality only at the most be Could be true.

They do talk alot about mixing up contra positives, but I really don't get how you could mix that up, and turns to or and it gets negated. However these contra positive inferences are important. I hope that first part made sense for you, I know its really hard to get (I was ready to quit the LSAT because of this lol) but just keep memorizing those indicators and looking how structures of sentences work. Think logical versus using common sense too! The workbook for the LR bible really helped me hone in and practice this further, if you have cash to throw around (not necessary if you don't have the money just helpful).

jre425 wrote:What I meant is by mixing up the sufficient and the necessary condition when you read a sentence. For example, if you a read a sentence that actually says A -> B (if A then B, contra positive is: if not B then Not A) as being B -> A (if B then A, contra positive is: if not A then not B) read competently different. Because the actual statement says that if A happens then you HAVE to have B, but if you have B it doesn't mean you have A or don't have A. But if you mixed the S and the N conditions around then it would read if B happens then A has to happen, but if A happens then B doesn't necessarily happen. As a result you will yeild incorrect answers because what you know as MBT (must be true) will in reality only at the most be Could be true.

They do talk alot about mixing up contra positives, but I really don't get how you could mix that up, and turns to or and it gets negated. However these contra positive inferences are important. I hope that first part made sense for you, I know its really hard to get (I was ready to quit the LSAT because of this lol) but just keep memorizing those indicators and looking how structures of sentences work. Think logical versus using common sense too! The workbook for the LR bible really helped me hone in and practice this further, if you have cash to throw around (not necessary if you don't have the money just helpful).

I seriously appreciate the help! And yeah, I think I got it now. Especially after reading what you said then looking back at what has been said in the LRB.

jre425 wrote:What I meant is by mixing up the sufficient and the necessary condition when you read a sentence. For example, if you a read a sentence that actually says A -> B (if A then B, contra positive is: if not B then Not A) as being B -> A (if B then A, contra positive is: if not A then not B) read competently different. Because the actual statement says that if A happens then you HAVE to have B, but if you have B it doesn't mean you have A or don't have A. But if you mixed the S and the N conditions around then it would read if B happens then A has to happen, but if A happens then B doesn't necessarily happen. As a result you will yeild incorrect answers because what you know as MBT (must be true) will in reality only at the most be Could be true.

They do talk alot about mixing up contra positives, but I really don't get how you could mix that up, and turns to or and it gets negated. However these contra positive inferences are important. I hope that first part made sense for you, I know its really hard to get (I was ready to quit the LSAT because of this lol) but just keep memorizing those indicators and looking how structures of sentences work. Think logical versus using common sense too! The workbook for the LR bible really helped me hone in and practice this further, if you have cash to throw around (not necessary if you don't have the money just helpful).

I seriously appreciate the help! And yeah, I think I got it now. Especially after reading what you said then looking back at what has been said in the LRB.

Glad it helped you, I'm just really starting too myself, a month or so in.